Case-hardening of metals.



PORTER SHIMER, OF EASTON, PENNSYLVANIA.

CASE-HARDENING OF METALS.

No Drawing.

To all whom it may concern:

Be it known that I, PORTER W. SHIMER, a citizen of the United States, residing at Easton, in the county of Northampton, State of Pennsylvania, have invented certain new and useful Improvements in Case-Hardening of Metals, (Case B;) and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

In an application ,for Letters Patent of the United States Serial Number 210,176, filed January 3, 1918, I have described and claimed the case-hardening of metals (for instance, articles of iron or steel") by means of a liquid melt or bath of fused salts (for instance, alkaline chlorids, chlorids of the alkaline earths, or alkaline chlorids and alkaline carbonates) which bath has been brought in contact with calcium cyanamid,' preferably by immersing the calcium cyanamid in the bath, in lump form and unchanged by atmospheric exposure.

As explained, in said co-pending application, the use of calcium cyanamid, inthe more or less air-slaked condition in which it usually appears on the market, is attended with the disadvantage that persistent overflowing frothing of the bath ensues,probably due, in part at least, to the presence of moisture in the air-slaked cyanamid.

So also, when powdered or pulverulent calcium cyanamid is introduced, as such, into the melt, each individual particle of the cyanamid is chemically acted upon with a number of great disadvantages. The first is a voluminous and persistent frothi'ng' or foaming. The second disadvantage is that, by the occasional necessary addition of fresh cyanamid, the melt finally becomes so thickened by the accumulating cyanamid mud as to become useless. A third disadvantage is that a part of the case-hardening gases are generated and escape from the surface of the melt without coming in contact with the articles to be case-hardened.

I overcome these difliculties as will hereinafter more fully appear by imprisonin or combining the particles of the powdere calcium cyanamid in what may be called a coke-sponge. This hard sponge allows the liquid melt to penetrate, act upon, and leach out the case-hardening properties of the cyanamid, without any foaming. The cokesponge also retains within its substance the Specification of Letters Patent.

Patented Sept. 1%, 1918.

Application filed January 8, 1918. Serial No. 210,177.

residuum which would otherwise constitute the cyanamid mud above referred to. This residuum is removed from the melt along with the spent coke in the basket. When alkaline chlorids alone are used in the melt,

a large amount of case-hardening alkaline cyanid is formed in the bath, and the evolutlon of gas is only moderate. When the chlorids of the alkaline earths are present there is a much more lively evolution of gases and the case-hardening effects are cor respondingly accelerated.

In carrying out the invention, air-slaked calcium cyanamid, if reduced to powder 1 form, and also powdered calcium cyanamid generally, may be used to advantage, if the powdered cyanamid be first mixed with a suitable binder,such as hard pitch (preferably pitch of such hardness that it can be pulverized and mixed with the powdered cyanamid, or of such a character that it can be ground to a pulverulent condition in the presence of the cyanamid). I have obtained good results by mixing three parts by weight of pulverized hard pitch with 7 parts of the powdered cyanamid, themixture being ef fected in a revolving mixing cylinder.

The mixture of cyanamid and pulverized hard pitch (or other suitable liquid or solid binder capable of coking, such as tar) is then subjected to a red heat for the time necessary to drive off practically all of the volatile matter from the coked mass. cooling, the coke-like mass is removed and broken into fragments of suitable size for After use,say 1 to 2 inches in diameter. The material, before coking, may also be formed into briquets of suitable size and shape for conamid referred to therein, and without froth- The liquid melt or bath of fused salts into which the fragments of the coke-like mass of the present invention are to be immersed or otherwise brought in contact, may consisr, for instance, of a fused mixture of sodium chlorid, calcium chlorid and barium chlorid, in equal proportions by weight, or

a fused mixture of two parts of Weight of sodium chlorid one part by weight of calcium chlorid, or of potassium chlorid, or Y of calcium cyanamid and binder are to be introduced. For instance, alkaline carbonates my be added in making up the liquidmelt.

The introduction of the fragments of the coke-like mass takes place to particular advantage if the fragments are placed in a basket of iron wire, said basket beingsuspended in the liquid melt at a location-near the bottom of the case hardening pot and in such manner as not to interfere with the use of the bath for the carrying on of the case-hardening operation. The articles to be case-hardened are preferably suspended in'the bath, as in the usual practice, upon suitable sustaining grids or the like, so as to be subjected to the best advantage to the action of the bath. v Qrdinarily, some time is necessary for the action of the bath upon the cyanamidcontained in the fragments of the coke-like mass, in order to develop in the bath the case-hardening properties. This time will vary from a few minutes up to say one half hour or more, according to the size of the bath. Thereadiness of the bath to do casehardening efi'ectively is indicated by a greater or less evolution of the gas from the bath. As soon as the gas begins to be actively evolved, the articles to be treated may be suspended'in the bath, according to the usual practice, and for the period of time desired. The case-hardening proper ties of the bath are best conserved by keeping the pot covered when not in use for casehardening.

I have found that it is not necessary to leave the basket containing thefragments of the coke-like mass continuously in the bath, but that after the removal of the basket andits contents the bath retains its case-hardening properties for a consider able time.

As indicated by a less lively evolution of the gas from the bath, when the alkaline earth chlorids are contained in! it, and eventually by a weakening of the case-hardening effect upon the articles to be treated, the case-hardening strength of the bath may be renewed by againfsuspending the basket with its contentsin the melt.

The quantity of the fragments of the coke like mass containing the cyanamid employed may be varied according to the size of the bath, the shape, size and character of the articles to be case-hardened, and other conditions, as Wlll be appreciated by those skilled in. the case-hardening art. I have added to the basket, from time to time, so

as to maintain its ability to give therequired" case-hardening properties to the melt. It is advisable to keep the basket and its contents in a dry place, during the interval of its periods of immersion in the bath, so that the calcium cyanamid may not become moist by attracting water from the atmosphere. It is also advisable to keep it dry and warm by hanging it over the bath'for' a short time before immersing it therein, in order to drive off any moisture which may be present in the cyanamid. The .gas which is evolved in the liquid melt by the action of the cyanamid, and whose evolution continues even after the cyanamid has been withdrawn from the melt probably contributes to the case-hardening properties of the bath to a considerable degree.

Th" basket of iron wire hereinbefore referred to wi11,of course, have wide meshes v so as to permit full and free accessof the liquid melt to its interior, and 1t will also have a like open mesh cover so as to prevent the fragments of the coke-likemass from tendency to rise to the surface of therbath, or-to otherwise pass out of the basket.

What I claim is:

1. The method of making a coke-like mass adapted for use in the case-hardening of metals, which comprises mixing calcium cyanamid with a suitable binder and coking the mass; substantially as described.

2. The method of making a coke-like massadapted for use in the case-harden1ng of metals, which comprises producing a mix-' time of powdered calcium cyanamid and hard pitch or other cooking binder, coking the mass, thereby driving off volatile gases and converting the mixture into a coherent body adapted to be molded or broken up into fragments of suitable size for u se.1n a casehardening operation; substantially as described. g

3. As a new composition ofmatter, a cokelikemass comprising calcium cyanamid associated with a binder substantially as described. 4:. As a new composition of matter, a cokelike mass, comprising calcium cyanamid associated with a coked pitch or tar; substantially as described.

In testimony whereof I affix my signature. 125

PORTER W. SHIMEB.

It is hereby certified that in Letters Patent No. 1,27 9,458, granted September 17,- 1918, upon the application of Porter W. Shimer, of Easton, Pennsylvania; for an improvement in Case-Hardening of Metals, errors appear in the printed specification requiring correction as followsi Page 1, line 112, the word of should read by; page 2, line 10, for the word my read my; same page, line 110, claim 2, for the word cooking read coking; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of v the case in the Patent Office.

Signed and sealed this 29th day'of October, A. D, 1918.

R. F. WHITEHEAD,

Acting Uomm'iss'ioner of Patente.

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